The invention relates to a compressor, in particular for use in the air conditioning system of an automobile, having a housing and a compressor unit accommodated in the housing for taking in and compressing a refrigerant. The refrigerant flows from an intake area in the housing cover through the compressor unit into a discharge area likewise formed in the housing cover, and the housing cover is sealingly connected to the housing via connecting members.
Compressors of the type described above are commonly referred to as air conditioning compressors and are known from practice in a large variety of configurations. Such compressors comprise a housing, which encloses an externally driven compressor unit or pump unit. The pump unit, which is designed and constructed, for example, as an axial piston pump, in turn comprises at least one piston, which is adapted for reciprocal movement in a cylinder block. Normally, such a compressor is provided with a plurality of pistons, which are reciprocated during the rotation of a swash plate via a receiving disk in the direction of their longitudinal axis, the receiving disk being supported for corotation in the housing.
In addition to conventional refrigerants, whose use appears to be more and more critical in the light of an increasing awareness of the environment, it is possible to use as the refrigerant an inert gas, for example, CO2, which is noncritical under environmental aspects. The use of such a refrigerant, however, requires higher pressures within the compressor, thereby necessitating very special constructional measures, for example, with respect to selecting material and dimensioning.
Normally, the housing cover is releasably joined to the housing of the compressor unit, with a valve plate being arranged therebetween. In particular in the case of CO2 compressors, which operate under high pressures, the connecting members are subjected to considerable stress as a result of the pressures prevailing in the interior of the housing. Thus, the enormous pressures occurring in the compressor unit or in the drive chamber, namely, pressures ranging from 40 bars to 60 bars, may lead to deformations of the connecting members, so that leakages result at the joint between the housing and housing cover. In this respect, conventional compressors make it necessary to provide additional, external sealing measures to be able to compensate at least slight deformations of the connecting members for avoiding leakages. This requires a more extensive constructional expenditure, and is inadequate to achieve the desired result.
It is therefore an object of the present invention to improve and further develop a compressor of the initially described kind such as to reduce the load on the connecting members that join the housing cover to the housing. Furthermore, it is intended to avoid at least to a greatest extent a pressure load on the connecting members resulting from internal leakages.
The above and other objects and advantages of the invention are achieved by the provision of a compressor wherein the connecting area, through which the connecting members which join the cover to the housing extend, is at least substantially separated from the high pressures generated in the compressor.
In accordance with the invention, it has been discovered that a load on the connecting members, in particular as a result of internal leakages, will be avoided at least to a large extent, when the connecting area is relieved from pressure. In other words, in the ideal case, the connecting area comprising the connecting members should be made pressure free, so that except for the axial load on the connecting members, no further load will occur, in particular there are no bending forces.
Advantageously, the connecting members extend through the housing cover into a peripheral wall of the housing. Also, a plurality of connecting members preferably are provided in equidistant relationship with one another along the circumference of the housing cover. Specifically, the connecting members could be screws, which totally extend through the housing cover, and engage with their external screw thread bores that are formed with a corresponding internal screw thread in the wall of the housing. When fastening or tightening the screws, the screw head comes to lie against the surface of the housing cover. This permits securing the housing cover to the housing in a sealing manner.
The pressure relief as further provided by the present invention could be realized by an inner seal against the outer connecting area, so as to ensure that the connecting area comprising the connecting members is more or less pressure free. Additional external sealing measure are not needed in the case of such an inner seal. Quite the contrary, the outer connecting area could include desired leakages toward the exterior, to be able to ensure to this extent likewise a further pressure relief in the case that an internal leakage occurs.
Seals may be arranged between the connecting area and the high pressure zone, both in the housing cover and in the housing. In the area, which is here referred to as the high-pressure zone, the drive chamber pressure is prevalent. Depending on the controlled position, this pressure is understood to be the intermediate pressure between the high pressure and the suction pressure. In this connection, it would be possible to seal the connecting area against the drive chamber or compressor unit, so that the connecting area is relieved from pressure or even free of pressure. In a further advantageous manner, the connecting area is likewise sealed against the high pressure zone in the housing cover. If a valve plate is provided between the housing or compressor unit and the housing cover, it will be of further advantage, when the connecting area is sealed against the valve plate, so that no pressure load may reach the connecting area either from the high pressure side inside the housing or from the high pressure side inside the housing cover.
The seals may be any desired rubber gaskets, for example, O-rings. Other conventional sealing measures are possible.
Furthermore with respect to a purposeful pressure relief of the connecting area, it will be of further advantage, when a pressure relieved space is formed between the connecting area and the compressor unit or drive chamber. This pressure relieved space preferably extends annularly around the compressor unit, and is provided in the vicinity of the engagement between the connecting members or screws and the housing peripheral wall. This space is suitable for compensating possible leakages from within the housing or from the drive chamber, at least to the extent that so-called creep pressures do not occur and act upon the connecting members to their full extent.
Furthermore, it will be of advantage, when the pressure relieved chamber is sealed against the compressor unit or against the drive chamber.
For a more extensive pressure relief of the space, primarily, however, of the connecting members, it will be of further advantage to provide at least one vent channel extending from the space toward the exterior of the housing, so that undesired leakages are able to escape from the space to the atmosphere, without forming pressure cushions relative to the connecting members, and thus having a negative effect.
There exist various possibilities of improving and further developing the teaching of the present invention in an advantageous manner. To this end, one may refer to the following description of an embodiment of the invention with reference to the drawing. In conjunction with the description of the preferred embodiment of the invention with reference to the drawing also generally preferred improvements and further developments of the teaching are described in greater detail.